Probably quite a lot of the failures are thermal issues.
As we all know, modern LED lighting is run way harder than it should be, in order to ensure an MTBF that keeps the factories in work.
There is information for the installer in the fitting instructions that tells you not to cover the top side, and how much air space is needed above it, but they are frequently installed by people that can't be arsed to read these things, either because "I've been an electrician for (insert suitable number) years, and I don't need to be told how to fit a light", or the younger ones who just don't give a toss.
I found Big Clive's recent vid on the "Dubai LED lamps" quite interesting. For sure when they start to sell them here, they will a) charge a premium, and b) find another way to bring the MTBF down.
Yes you're right, there are some extremely clever electricians out there. I once had to drop everything and make a quick dash from London to the Metro Centre in Newcastle upon Tyne and back on the same day. A contractor fitting out a T Mobile shop was using the specified lighting control system which was dumb marshalling boxes with some plug-in semi intelligent control modules that used plugin logic blocks and a 6 and 4 core data cables (RJ25 and RJ14 plugs) to connect the control modules in together in various ways to form circuits / groups / functions as required. It was reported that 1 day prior to hand over the contractor had decided to test the lighting and only 1 marshalling box was working.
When I arrived I walked into the back storeroom and discovered all the instructions along with my schematic for the installation in a heap of rubbish that was being chucked into a skip by the loading bay. The contractor confessed that he never looked at any of them as he had done commercial lighting many times before, that was his first mistake.
Opening up the only working marshalling box, My suspicions were confirmed, the mains supply was supposed to be looped from the first box onto the others, but there were no cables between marshalling boxes other than the data cable. The Contractor said that he thought the mains was carried between them via the data cable
All the cables were neatly attached to a suspended ladder tray. I got him to run mains cables between them while I set to plug in the correct logic blocks in the right order to provide the level of control that T-Mobile specified for their shops. Within a short space of time it was all up and running correctly and when the T-Mobile inspector and other top staff turned up for the hand-over, it all went smoothly.
That was not an isolated incident either, had others along similar lines at Oxford Street in London and another in Dartford shopping mall. Where do they find their contractors FFS